1. Field of the Invention
This invention relates to hydraulic shearing machines employed for shearing steel sheets or the like.
2. Description of the Prior Art
Shearing machines of this type comprise two blades, namely a lower blade fixed between two vertical end-plates of the frame and an upper blade carried by a movable apron. When seen from the front, the upper blade is placed obliquely in order to be inclined on one side and thus to ensure that a shearing operation to be performed on a steel sheet begins near one edge of this latter and continues toward the other edge, progressively as the apron moves downwards.
In current shearing machines of this type, the lower blade is fixed against the top edge of a vertical apron which extends between the two end-plates of the frame, said apron being rigidly fixed to a horizontal table which is intended to support the steel sheets to be sheared. During operation of a shearing machine of this type, however, reactions of resistance to cutting are exerted in a vertical direction and in a horizontal direction. These reactions have a tendency to cause horizontal and vertical flexural displacements of the stationary and movable aprons. However, the vertical flexural displacements give rise only to simple problems of resistance to bending stresses, or fatigue strength.
The horizontal flexural displacements, however, have a tendency to separate the two cutting blades horizontally. In consequence, the clearance between these blades increases, thus modifying the cutting geometry and giving rise to an increase in the horizontal reaction. The system is therefore cumulative and produces poor cutting results (mainly rough edges and burrs).
For this reason, the object of the present invention is to provide a shearing machine which is so designed as to reduce the clearance between the cutting blades in order to obtain good cutting conditions.